calculate opening and closing trade receivables
trade receivable turnover ratio -  4 times
cost of revenue from operation - 640000
gross profit ratio - 20%
closing trade receivable is 20000 more than opening trade receivables.

Hi Anindita,

The information provided by you seems to be incomplete. It must have also been given that cash revenue from operations (cash sales) is $33\frac{1}{3}\%$ of credit revenue from operations (credit sales).

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https://www.meritnation.com/ask-answer/question/calculate-opening-trade-recievable-and-closing-trade-recieva/accountancy/6570414